Supporting structure for gas turbine power plants



Oct. 21, 1952 a. B. R.-FE|LDEN SUPPORTING STRUCTURE FOR GAS TURBINE POWER PLANTS 7 Sheet s-Sheet 1 Original Filed Jan. 14, 1946 GEOFFREY B. R. FEM-DEN Inventor Aftorz ley Original Filed Jan. 14, 1946 Oct. 21, 1952 e. B. R. FEILDEN 2,614,335

SUPPORTING STRUCTURE FOR GAS TURBINE POWER PLANTS 7 Sheets-Sheet 2 FIG. lA.

GEOFFREY B-R. FaaLo'sM Inventor mud! B W Attorney Oct. 21, 1952 e. B. R. FEILDEN 8 SUPPORTING STRUCTURE FOR GAS TURBINE POWER PLANTS Original Filed Jan. 14, 1946 '7 Sheets-Sheet 3 G20 "Rev B. R. FEM-DEN Inventor Attorney QMRQW Oct. 21, 1952 G, B. R. FEILD EN 2,614,335

SUPPORTING STRUCTURE FOR GAS TURBINE POWER PLANTS '1 Sheets-Sheet 4 Original Filed Jan. 14, 1946 MOE I IAAAAA\ .1\\\\\\\\\ GEOFFREY B. R. FEILDEN k I555 WWI-f a Ill/III Inventor Oct. 21, 1952 e. B. R. FEILDEN SUPPORTING STRUCTURE FOR GAS TURBINE POWER PLANTS '7 Sheets-Sheet 5 Original Filed Jan. 14, 1946 GEOFFREY 8.12. Farms/v.

Inventor Attorney Oct. 21, 1952 2,614,385

SUPPORTING STRUCTURE FOR GAS TURBINE POWER PLANTS G. B. R. FEILDEN 7 Sheets-Sheet 6 Original Filed Jan. 14, 1946 G EoFFREY B. R. FEILDEN Inventor Attorney Oct. 21, 1952 G. B. R. FEILDEN 2,614,385

- SUPPORTING STRUCTURE FOR GAS TURBINE POWER PLANTS Original Filed Jan. 14, 1946 7 Sheets-Sheet 7 O N I p n s: 1

n n {3 '0. o m U n GEoFkREv B. R. Fauna lnvenlor Q Afforne y tributes are desirable.

ternal components should be facilitated.

Patented Oct. 21, 1952 UNITED STATES PATENT orr cs" SUPPORTING STRUCTURE FGR GAS TURBINE POWER PLANTS Geoffrey B. R. Feilden, Canwick, Lincoln, England, assignor to Power Jets (Research and Development) Limited, London, England, a company of Great Britain I January 16, 1945 unit driven by the turbine and accommodating in the space between them a combustion system through which working fluid. is supplied by the 1 Claim. (01. (so-49.37)

compressor to the turbine with the general direction of flowin an axial direction. Where such a machine is to be used as a-power unit, for ex ample for the propulsion of aircraft, various at- For example the unit should be kept as compact and as light as possible,- while maintenance and replacement of components and probably periodical inspection of in- It is also desirable that the disposition of parts which are liable to fluctuations of temperature or which operate with a temperature gradient through them should be such as to allow for or cope with relative expansions and contractions, and distortions, without adverse effect. The various aspects of the present invention seek to provide suchattributes as well as Others. Particularobjects of the invention as applied to a gas turbine power unit for aircraft are, to achieve a symthe actual combustion takes place arranged within and annularly distributed around said aircasing.

In association with this conception, in accordance with the invention the inner wall of said annular aircasing is formed as a stiff member which is structurally integrated with the stationary structure at adjacent sides of the compressor and turbine to form therewith a substantially rigid unit andperforms the dual function of defining the boundary of the fluid channel enclosing the driving shaft and forming a rigid backbone structure serving as a major stress carrying element of the stationary structure unifying the compressor and turbine sections of the unit.

According to a further feature of the inven tion, the outer wall of the annular aircasing is also of unitary circular structure attached to the compressor and turbine stationary structure and forming a supplementary stress-carrying element of the structure unifying the, compressor and turbine sections of the unit. v

In a preferred application, the various features of the invention arev embodied, in a gas turbine power plant comprising a multistage compressor with air outlets arranged symmetrically about its shaft axis and'directed in a general senseaxially, and an axial flow turbine spaced axially from the compressor and in tandem therewith.

While the aircasing walls will/normally be of circular cross section, and the space between them truly annular, the use of other equivalent An,- example of application of thejinvention will now be described with-"reference to the accompanying drawings, which illustrate by wayof Figures 1 and 1A constitutetogether an elevation in half longitudinal section'showing the general arrangement of an aircraft jet propulsion gas turbine power unit embodying the invention in one constructional form;

Figure 2 is a detail sectional elevation to an en.- larged scale illustrating the construction of the aircasing of the power unit illustrated in Figure 1,

on a burner;

Figures 4 and 4A together constitute an elevation of another jet propulsion gas turbine power unit illustrating the general arrangement thereof in part longitudinal section in the region of the aircasing, which is of a modified form as compared with Figure 1;

Figure 5 is a detail sectional'elevation to anenlarged scale illustrating the modified construction of aircasing and construction and mounting of flame tube combustion elements embodied in Figure 4A.

Certain features of the units illustrated also form the'subject of co-pending applicationNo. 64l,144'filed"January 14, 1946, of whichthis application is aidivisionc In the example illustrated in Figure l, the power units comprises generally a multistage axial compressor I, an annular combustion arrangement 2, a turbine 3 exhausing into a reaction jet passage 4, a thrust-augmenting ducted fan 5 associated with the turbine 3 and operating in a supplementary reaction jet passage 6 coaxially surrounding the passage 4, and a shaft 1 common to the compressor I and turbine 3 through which the latter drives the former, and with respect to which the entire engine is arranged in a symmetrical circular man ner, the said shaft incorporating a flexible coupling Ia having resilient flange elements and a tension element which resists the opposed end thrusts developed by the compressor and turbine. The forward end of the unit when installed, is enclosed by a fairing 8 as may be appropriate to the aircraft concerned. At the forward end of the compressor is carried a gear box for driving accessories which derives its powerfrom the shaft 1.

The compressor 1 has a rotor built up from a plurality of separate discs each carrying peripher'ally a'row of compressor blading, while the stator blades extend inwardlyfrom an'outer casing 9 which, with thefront and rear walls "I0, I l, in which bearings are provided for the shaft 7, defines an annular inlet at Hand outlet at l3, of whichfthe latter is'extencled axially by inner and outer annularjwalls l4, which, with radial walls 16 'therebetween form a series of axially directed diffuser channel'sall opening at an'annulus defined by "two concentric flanges of the Walls ('4, I5. To'the inner flange (see'more'parlti'cularly Figure 2) is attached a hollow member 'l'l 'off'circular cross "section which encloses the shaft 1 [and 'extends'coaxially therewith towards the'turbine 3. Towards its'rear end, the member If! is rigidly attached to "the apex of a frustoconical member IB'the rearward or base rim of which provides the inner support of'the turbine entry nozzle annulus 'l9,'between which and the inner'wall of thepassage'fi is a frusto-conical bracing annulus iBa'.

In the construction illustrated, thev turbine, generally indicated at 3, comprises a first or compressor-driving turbine having two axially spaced 'blad'ed'rotors 20 fast on the shaft hand a second turbine having one bladed rotor 2| 'Which is arranged forwardly of the rotors 2,0 and has a bearin sleeve 20a by which it is rotatably mounted through axiallyspaoed bearings 20b on a tubular member forming in effect a" rearward extension 'I'Tg of the member I! already referred'to, the

said extension i'laand member I'Tbeingin turn spaced fromthe shaft 1 and supporting it by axially spaced bearings llb as indicated. The blading of the rotor 2| is connected to a peripheral rim 22 which extends rearwardly to form both a tip shroud 'forthe blading of the rotors 20, and a support fora second ring of blades 21a of "the second turbine, these blades extending radially inwardly, like interstage stator blading.

There is no fixednozzlering or interstage-stator blading associated with the first turbine, the

function of such parts beingperformed by the first and second rows of bladin'g of the second forward end is supported on the rimf22. of the second turbine by a frusto-conicalmember 24, and whose stator blades 51) arefixed to the main around the nozzle.

structure of the ducting forming the passage 6, the inner wall of which is braced from the nozzle ring of the second turbine by the frustoconical member l'8a. It follows from this construction that the torque of the second turbine is transmitted outwardly to the fan drum 23 so that the fan will augment the flow of air in the duct '5 derived from the forwardly facing entry. The ducts d, 6 unite at some distance aft of the fan 5 andinthe intervening length of the duct 6 fuel combustion means 26 are provided further to energise the airflow, preferably so as to accelerate it to the velocity of the turbine exhaust stream in the passage 4 before the two streams emerge as a single propulsive jet.

The hollow member I! constitutes the inner air pressure-sustaining wall of anaxially extending annular aircasing, the outer air pressure-sustaining wall of which is formed by a tubular member 2'! detachably secured at its forward end to the outer'fiangeof the compressor outlet annulus defined by the-walls l4, l5 and'at its rear end'toa frustoconical member 25 whose apex is secured to the turbine nozzle ring -9. The memberZ-I'is of such internal diameter that when-its fastenings are released it may be slid forwardly over the compressorcasing 9. 'The 'members 21,41, have mounted thereon in spaced"relationship, thereto, sheet metal liners 28, 29, to provide an air jacket for the inner and-outer walls of "the aircasing, these liners being arranged at their ends to pick up a proportion of the incoming air streamand discharge it to theturbine after'flowing through the respective air'jackets. In this connection, in'order that it shall not interfere with the'axial withdrawal of the outer wall 21', the liner '28 makes loose overlapping joints with liner parts 28a which are mounted on parts of the structure which remain fixed when the member 21 is removed. I 1

Between the walls l1,27, and in the annular cavity they enclose,is provided an'annu1arly-arranged series of axially extending flame tubes so dimensioned as to permit freedom of airflow around and among them. The main body 30-of each flame tube is cylindrical and has at its upstream end a frustro-conical-closure whose-apex engages axially with, and is supported by, the protruding end of a 'cyli'ndrically shapedburner or fuel nozzle 3|"which is coaxial with the flame tube and is mounted upon one of the diffuser walls [6 of the'compressor outlet annulus. A suitable form of such a construction is illustrated in Figure 3, in which the burner body 3l is boltedto one of the diffuser 'walls I6 of the compressor outlet annulus in'reg-ister with'fuel supply'connections iila provided in thebody of the wall 16 and registering also with a fuel pipe connection element 3 i b accommodatedin a passage 3'lc extending radially through sai'd'wall, which-incidentallv aiso affords an air passage between the chamber enclosed by'the'inner side'of said'com pressor annulus and the outside atmosphere. The flame tube isretained against'involuntary displacement by making threaded engagement with the nozzle 3 l' as shown, or by others-u-itable means, and provision-is made by apa'ssa'ge 'fld for the entry of combustion air through and The flame tube wall is 1 also perforated and provided; with appropriate guides and baffles as may, be found necessary for :combustion. The downstream end of the cylindrical 'body'3G of the tubejis supported'for example by flexible tie memberstflaconnected'to the liner 29,

so as to lie just within-andspaced from the circular'upstream-end of an outlet chute 32 which tapers in-the downstream direction to aflattened section corresponding to a segment of the annular nozzle ring IQ of the turbine. Thismethod of flame tube suspension is the subjec't of copending patent application No. 647,381 filed February 13, 1946, now Patent No. 2,511,432. Space is left 'around'the Outside of each outlet chute 32 for the passage of some air to theturbine nozzle so that this air cools the-wallof the chute and, being itself heated in the process, ultimately joins the hot gases which are entering the turbine. The chute 32 is located and supported by 'a substantially radial strut-like element 33 passing therethrough and also through the liners 28a, 29, and inner and outer aircasingmembers I8, 25,

'to all of which parts the strut is secured, as by welding. Preferably the primary purpose of the struts 33, which'are provided at intervals'around the annulus of the aircasing, is to maintain the concentricity' of the aircasing parts 18, 25, but they may alsobe made hollow and thus provide a communicating passage between the space enclosed by the member I8 and the outside of the aircasing permitting a flow of cooling air through thestrut.

Alternative methods of'supporting the outlet chute 32 may be adopted, but in; anycase the supportis so contrived as to'permit longitudinal and radial expansions without. bodily displacement of the flametube and without imposing specific stresses thereon oron 'anyof the related parts.

To remove any flame tube body 33, the outer wall 21 of the aircasing is cast loose and displaced axially over the compressor casing 79,

and the flame tube body; shifted axially towards the turbine to free itvcompletely from theburner (a movement which is allowed for in the spacing of the downstream end of the body 30 from any axially obstructing parts)- The body 30 may then be tilted sufliciently to allow it to be withdrawn.

As an alternative the flame tube body 30 may be left attached tothe burner, and the latter unbolted so that it can be withdrawn from its mounting by the axial movement of theflame tube. In either case, the burner itself is in essence the support of the flame tube at its upstream end, while the means which relate ;it;to

Ithe outlet chute or to the main aircasing structure (which permit expansion) are the support at the other end. .2 -In addition to forming the air pressure-sustain- =in'g walls of an annular aircasing, the outer of l which, as to its greater part, isaxially removable bounded at its rearward end by the turbine rotor lends itself admirably to the provision of a distributing system for cooling air, additional to that already referred to in connection with the internal construction of the aircasing and flame tubes, which will assist in avoiding gas leakage, local distortions and excessive local temperatures, and to a considerable extent render uniform the tem-. perature distribution throughout the engine. One such system is illustrated in Figures 1A and '2, in'which the wall formed by the inner member I! of the-aircasing is made hollow and, being connected 'by'a pipe 35 to a suitable point on the compressor to receive compressed air therefrom, distributes it as indicated by the arrows in Figure 2.- The hollow-wall of the member I? forms air passages 36 (see Figure 2) which are connected to the'turbine'bearing housing and also'to the chamber bounded by the member I8 and the face and journal sleeve of the turbine rotor 21 and with the space between the rotors 2|, 2!). Said chambercontains a stationary sheet metalliner 31 of annular form which constrains the air flow to-followthe surface of theturbine rotor parts, the air eventually escaping through theflame tube struts 33'tothe inlet of the augmenter duct. In addition, the shaft 1 is made hollow and'transmits air to the inner and rear faces of the rotors 20, whence it escapes to the turbine gas stream. The air coming direct from the compressor is arranged to be ata slightly higher pressure than that'in the turbine so that the tendency is for the air to flow into the turbine rather than for gas to escape from the latter.

' By means of the air systemsdescribed above, or modifications thereof, the various cavities and regions of the engine may be supplied with compressed air in such a way as to effect cooling and I oppose any tendency to gas leakage, although gas seals will still be employed where necessary.

In the construction of aircasing illustrated in Figures 1 and 2, the inner members l1, l8, and the outer member 25, are formed by relatively substantial castings; according to a furtherfeature of theinvention these parts are fabricated from sheet metal whilenstill retaining the features that the aircasing, in addition to being the airpressure-sustaining element of the combustion arrangement, constitutes a major stresscarrying structure forming with the compressor and turbine casings a substantially rigid-unit.

Such a modified form of aircasing is illustrated in Figures 4 and 4A in which parts similar to those in Figures- 1 and 1A have like reference numerals, as applied to another. form of power unit from that appearing in Figures 1 and 1A and which, apart from the aircasing construction, differs Itherefrom. principally in that the compressor'output passes first through outwardly directedpassages 50 to a two-part outlet annulus 5l= before being discharged in a generally axial direction into the combustion arrangement; that the contrarotating rotor of the turbine and-its associated ducted fan augmenter are omitted; and that the forward end of the shaft 1 is used to drive, through a concentric epicyclic reduction gear, the coaxial shafts of a pair of contrarotating airscrews.

The aircasing in this instance comprises an inner member I! of frustro-conical form having internal strengthening ribs 53. The said inner member I! is supported at its forward end by oppositely tapering radially inwardly and outwardly directed frustro-conical elements 54, 55 secured thereto and to the rear wall ll of the compressor housing, and at its rear end by a somewhat similar arrangement of frustro-conical elements 56, 51 of which the inner one is secured to the housing of the turbine rotor bearing 58 which, as in Figure 1, is arranged forwardly of the rotor for the better access of cooling air, and

to' thelou-ter part'of the turbine nozzlering 19. v

Each .of the mentioned parts of the aircasing is fabricated ..from relatively thin sheet metal .to tormza tubular or dished annular elementof considerable stiffness-so that when they'are united a backbone :structure is obtained having a high degree 10f rigidity "combined with light weight whichmhensecured-to the compressor andturbine,: forms therewith a substantially rigid uni-t.

Where a sheet metal element is to bejoined to :an'other part, it is provided With a thickened flange, as indicated the drawing, by welding onto the sheet'metal'a strip of more substantial metal.

As in the embodiment. illustrated in Figures 1 and lAthe outer wallZ"! of the aircasing is axiallyiremovable, although in this caserearwardly, to expose the combustion system, which'again comprises a series of flame tubes spaced around the. hollow annulus formed by the'aireasing. As before, the flame tubes comprise a generally cylindrical body 30 forwardly closed by a conical end engagingzthe fuel burner or nozzle 3| and supported at the :rear endx'by an Outlet chute 32 positioned by ahollow. strut 33 passing therethitough. 'In place'of the complete air-ja-cketing of a the Jaircasing by. liners corresponding to those initheprevious c0nstruction,.the compressor discharges through sheet "metal outlet nozzles '60 which at their upstream ends'are of'fiattene'd *section-tofit asegmentofthe annular outlet of the compressor, :and merge downstream into a cylindrical shape which encloses 1 for a substan- 'tial'rdistance the upstream "end of one flame tube andis space'difrom it to allow therpassage of air.

The "flame :tube arrangement "just described againlprovides for the ready individual removal :of-ithe tubes after access theretohas been obtained "by displacing the outer wallz2l the method of removal being'the same as described in relabody being made such that when this has been :Edonebothnozzle and body ::can be stilte'd :out-

'wa-rdly without fouling the burner'3 I.

'rAnfeature of the design illustrated in? Figures E k-4A and '5' is that the entire inner; chamberv defined by the members L1, 54, 55 is; maintained under; pressureinorder to compensate for theex-r ternalpressure inthe annular'aircasing. By this means,-the sheet metal inner structure 4.1, :54, 5.5, maybe rmade ;much lighter, and with less attention to inner stiffening, than would other-- wise-be theca'se; iniaettheflfeature:ie ohgrgeat importanceini enabling the maximum advantage tosbetaken of the lightness of structure offered byzthezuse of sheet-metal. -Byg.providing suitable outlets, compressed ;air within :the 1 said inner Ghamber may 'be utilised to provide air cooling circuits, such as those indicated by arrows-inthe drawing, "-to :the compressor and -turbine rotors and the :shaft bearings. As indicated-in the drawing, the internal pressure may be -..obtained by tappingair under; pressure iromlthe aircasing by means of-apipel connected to theinner chamber, the air passing through a cooler 2.

TI claim: v .-A gas turbine vapower plant comprising za-ccmpressor assembly including a compressor rotor and 22,11 enclosing :compressor stationary :struc ture whicheincludes-a Wall onthe downstream side of the compressor :rotor; a turbine I assembly including a turbine rotor coaxial with rand laxially spaced .from the compressor rrotoriand an enclosing nturbinef stationary structurewhich .in- :cludes-;a*- wall: onithez upstreamisideoft-hetturbine rotor 2a driving shaft rcarrying :saidrrotors ibearingstmounted insaid walls. in:-the;compressor;and turbine stationary g-structures and supporting said shaft; and a combustion system lying be: tween :the compressor and turbine :assemblies and including an;aircasing :formed;by:an inner and "an outer tubular axially: extending wall icoaxially surrounding .:said "shaft, :the aircasing forming avpathzfor workingjfiuid from thecompressor to the'turbineextending generally in :an axial 'direction, =.and -at least one flame tube within the airca'sing; said inner wall ibein'g :a unitarystruc'ture and rigidly attached-at its ends to-saidcompressor and-turbine stationary-structures to formthe backboneof thelplant.

GEOFFREY B. R. FEEDEN.

liKEEERENGES CITED I-Ioward 'Aug.;23, 1949 

